The present invention relates to the dissolution of single walled carbon nanotubes in solutions and more particularly, to a method of dissolving naked single walled nanotube carbon metals and semiconductors in organic solutions.
All previous work on carbon nanotubes (both single-walled and multi-walled), has been carried out on the usual intractable, insoluble form of this material [Yakobson, B. I.; Smalley, R. E., Fullerene Nanotubes: C1,000.000 and Beyond. American Scientist 1997, 85, 324-337.] This form of the material is not amenable to many of the processing steps that are necessary if the single-walled carbon nanotubes (SWNTs) are to reach their full potentialxe2x80x94particularly in applications that require these materials in the form of polymers, copolymers, composites, ceramics and moldable forms.
While present forms of the SWNTs can be heterogeneously dispersed in various media, the interactions between the SWNTs and host and between the SWNTs themselves are simply physical, and without the formation of chemical bonds. Thus, the advantageous properties of the SWNTs are unlikely to be realized on a macroscopic level. What is needed is a method to prepare well-dispersed forms of SWNTs perhaps by inducing them to exfoliate from the bundles and dissolve in organic solvents. Although long believed to be impossible, [Ebbesen, T. W., Cones and Tubes: Geometry in the Chemistry of Carbon. Acc. Chem. Res. 1998, 31, 558-566] we now teach such a procedure for the dissolution of SWNTs [Chen, J.; Hamon, M. A.; Hu, H.; Chen, Y.; Rao, A. M.; Eklund, P. C.; Haddon, R. C., Solution Properties of Single-Walled Carbon Nanotubes. Science 1998, 282, 95-98].
The present invention relates to solutions of single-walled carbon nanotubes dissolved in an organic solvent. Such solutions are anticipated to be useful in determining the functionalization chemistry of the open ends, the exterior walls or convex face and the interior cavity or concave face of single-walled carbon nanotubes and processing useful nanotube based polymer, copolymer and composite products and devices for a multitude of applications in various industries including aerospace, battery, fuel cell, healthcare and electromagnetic radiation shielding.
Advantageously, as a result of the present invention, functionalization chemistry of the SWNTs can be determined through the study of both the ionic and covalent solution phase chemistry with concomitant modulation of the single wall nanotube band structure.
Additional advantages, and other novel features of the invention will be set forth in part in the description that follows and in part will become apparent to those skilled in the art upon examination of the following or may be learned with the practice of the invention. The advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.
In accordance with the purposes of the present invention as described herein, a novel and improved method of dissolving single-walled carbon nanotubes and semiconductors in common organic solutions is provided. In one possible embodiment, the method comprises purifying the single-walled carbon nanotubes and terminating open ends thereof with carboxylic acid groups. This may be followed by shortening the single-walled carbon nanotubes to a length of between substantially 1-1000 nm. Next is the polishing of the single-walled carbon nanotubes. Then follows the converting of the carboxylic acid groups on the open ends to acid chloride groups. This is followed by the reacting of the single-walled carbon nanotubes with an amine or alkylaryl amine having a formula RNH2, or R1R2NH wherein R, R1 and R2=xe2x80x94(CH2)nCH3 where n=9-50 or R, R1 and R2=xe2x80x94(C6H4) (CH2)nCH3 where n=5-50. The final step is the dissolving of the reacted single-walled carbon nanotubes in the organic solvent. In the method, RNH2 may be a compound selected from a group including octadecylamine, 4-dodecylaniline, 4-tetradecylaniline and any mixtures thereof.
In yet a second possible embodiment, unshortened single walled carbon nanotubes are dissolved in common organic solutions. This is accomplished by eliminating the shortening step.
In a third possible embodiment, the carbon nanotubes"" open ends are reacted with long chain amines, eliminating the step of terminating the open ends with carboxylic acid groups. This is followed by the reacting of the single-walled carbon nanotubes with an amine or alkylaryl amine having a formula RNH2, or R1R2NH wherein R, R1 and R2=xe2x80x94(CH2)nCH3 where n=9-50 or R, R1 and R2=xe2x80x94(C6H4) (CH2)nCH3 where n=5-50. The final step is the dissolving of the reacted single-walled carbon nanotubes in the organic solvent. In the method, RNH2 may be a compound selected from a group including octadecylamine, 4-dodecylaniline, 4-tetradecylaniline and any mixtures thereof.
In accordance with yet another aspect of the present invention, novel solutions are provided comprising single-walled carbon nanotubes dissolved in organic solvents. The organic solvents are preferably aromatic or chlorinated solvents. Solvents in which the SWNTs of the present invention may be solubilized include but are not limited to chloroform, dichloromethane, benzene, toluene, chlorobenzene, dichlorocarbene, ether, tetrahydrofuran, trichlorobenzene, methylene chloride, diethylene glycol, dimethyl ether, carbon disulfide, tetrachlorocarbon, pyridine, quinoline, dichloroethane, diethyl ether, xylene, naphthalene, nitrobenzene and mixtures thereof. The single-walled carbon nanotubes dissolved in the organic solvent when shortened have a length between 1-1000 nm and a diameter between 0.5-100 nm and are connected via amide linkages to branched or unbranched alkyl chains of 5 and more preferably 9 or more carbon atoms in length.
Advantageously, such a solution not only allows the study of the functionalization chemistry of the open ends, the exterior walls or convex face and the interior cavity or concave face of the nanotubes, but also processing of the nanotubes into useful products for various applications including as intermediates in the preparation of polymer, copolymer and composite materials.
Still other objects of the present invention will become apparent to those skilled in this art from the following description wherein there is shown and described a preferred embodiment of this invention, simply by way of illustration of one of the modes and alternate embodiments best suited to carry out the invention. As it will be realized, the invention is capable of still other and different embodiments, and its several details are capable of modifications in various, obvious aspects all without departing from the invention. Accordingly, the drawings and descriptions will be regarded as illustrative in nature and not as restrictive.